Design a Video Processing Pipeline, stage 1 of 14: model
Read the requirements like an engineer
Before choosing anything, turn the brief into numbers. Two of them decide most of this design: how long a large upload takes over an ordinary connection, and how many transcodes are in flight at once.
Useful arithmetic: 1 GB is 8 gigabits. Little's law says the average number of jobs in a system equals the arrival rate times the time each job spends there (L = λW). It holds for any stable system regardless of how arrivals are distributed.
Decide whether each statement holds, fails, or depends on something the brief has not settled.
System so far· 3 parts
Select a component to see what it is responsible for and which state it owns.
- 1Instructor browser → Video API: Create upload, report parts, poll status
What you need to know
Network speeds are quoted in bits per second; file sizes in bytes. One byte is 8 bits, so 1 GB is 8 gigabits. To get a transfer time, convert the file to bits and divide by the link speed.
Work it out
A 4 GB file uploads over a 20 Mbps home connection. About how many minutes does it take?Little's law: the average number of jobs in a system equals the arrival rate times the time each job spends there.
L = λ × WIt holds for any stable system, whatever the pattern of arrivals. It turns "how many per second" and "how long each" into "how many at once", which is the number that sizes a worker fleet.
Work it out
Sunday peak: about 0.12 uploads arrive per second, and each transcode takes 750 seconds. How many transcodes are in flight at once if nothing waits?Check
A worker dies 14 minutes into a 20-minute transcode. The requirement says accepted uploads are never lost. What does that force?